Electrostatic pumps operating without any moving parts have been known e.g. from U.S Pat. No. 4,634,057, from U.S. Pat. No. 3,398,685, as well as from U.S. Pat. No. 4,463,798 for a fairly long time. Such electrostatic pumps have at least two electrodes spaced apart essentially in the pump flow direction, the fluid (liquid or gas) to be pumped flowing around the electrodes. The electrodes are adapted to have applied thereto a d.c. potential or an a.c. potential so as to inject an ion current flowing between the electrodes through the fluid. The gases or liquids which are adapted to be pumped by means of an electrostatic pump are media, which are essentially non-conductive and which normally have a resistance value in the order of 10.sup.7 to 10.sup.10 ohm cm. The ions injected into the fluid by the electrode, which is normally provided with a sharp tip, run through the fluid upon moving to the opposite electrode. This relative movement of the ions in the fluid to be pumped produces the pumping action of such an electrostatic pump, which, consequently, is capable of functioning without any moving parts.
Typical electrostatic pumps according to the prior art, which is established, e.g., by U.S. Pat. No. 4,463,798 or by U.S. Pat. No. 4,634,057, consist essentially of a tubular housing member, which is constructed such that a fluid can flow therethrough in the axial direction and which is provided with a first centrally arranged electrode in the form of a cone tip arranged at an axial distance from the counter-electrode, such distance being normally adjustable by means of a thread, and the counter-electrode consisting essentially of a nozzle provided with a recess in the form of a truncated cone. The typical housing member of the known electrostatic pumps is made of plastic material. The electrodes, which consist of metal, are normally screwed into the housing member. The known electrostatic pump having the structure described not only requires comparatively high operating voltages in the order of 15 kV to 40 kV, but it also requires a complicated adjustment in order to set an appropriate electrode spacing. In addition, the structural design of the known electrostatic pump precludes any far-reaching miniaturization of such pump so that the possible fields of use of the known electrostatic pump are restricted.
U.S. Pat. No. 3,267,859 disclosed an electrostatic pump provided with a cylindrical housing of plastic material having arranged therein two spaced metal electrode plates whose electrodes have a web-shaped or edge-shaped cross-sectional configuration. This pump is not suitable for the purpose of microminiaturization.